ZeeOSix

I heard that GM has a fixed orifice PCV "valve" unit that will fit into the rubber holder of the original PCV valve for 2003 or older Vettes.

Has anyone used the fixed orifice PCV unit in place of the original valve to see if it makes any difference in the amount of oil in the intake system and/or catch can if you run one?

Anyone know the GM part number for this new PCV “valve” unit?

thetorch

I haven't used one, but here is some information on it.

EXCESSIVE OIL CONSUMPTION
GM offers a modified PCV valve to address customer complaints of excessive oil consumption on the following applications equipped with 4.8L, 5.3L or 6.0L engines:
1999–2002 Chevy Silverado, Suburban and Tahoe, 1999–2002 GMC Denali, Sierra, Suburban and Yukon, 2002 Chevy Avalanche, and 2002 Cadillac Escalade and Escalade EXT.
Excessive consumption would involve a vehicle that consumes one quart of oil per 2,000 miles. This is assuming the vehicle is a personal use, non-commercial type vehicle driven under normal conditions. Obviously, vehicles that are used in extreme service, such as heavily loaded trucks, or vehicles driven at high rates of speed would not be included, as their oil consumption rates may vary. Important: A minimum of a 4K mile engine break-in period should be performed, prior to condemning an engine for excessive oil consumption. Some basic checks that should be performed first include:
1) Inspect the top and lower engine components and covers for evidence of leakage.
2) Verify the proper dipstick is being used and that the tube is secured in the engine.
3) After engine shut-down, allow five minutes for oil drain-back, prior to checking the oil level.
4) Make certain the vehicle is sitting in a level position when checking the oil level.
5) Has the vehicle been driven at excessive speeds?
6) Has the vehicle been heavily loaded or pulling a loaded trailer or camper?
7) Is there evidence of engine overheating?
Assuming that the basic checks and considerations have been satisfied, GM recommends installing a revised PCV valve. It has been determined that under certain operating conditions, the original equipment variable type PCV valve flow rate may promote excessive oil consumption. The original equipment valve may promote a siphoning of the oil back into the intake manifold where it would be consumed through the combustion process. Examine the hose that attaches the PCV valve to the intake manifold for evidence of an excessive amount of oil. If excessive oil is present, GM recommends installing a revised PCV valve. The new style valve (GM #12572717, Mighty #3-932) is a fixed orifice valve with no moving parts (see illustration). The valve will not rattle when shaken. It is basically a shell of the OE style valve with an approximate .100 inch hole drilled in the bottom of the valve, providing a fixed flow rate. When servicing, technicians must be aware of the factory modification and be certain not to install the same type variable orifice valve that originally came on the vehicle. Doing so would reintroduce the performance condition that was corrected with the fixed orifice design.

ZeeOSix

Great info ... thanks!

I didn't see the Vette engines listed in the application list, but I bet it's the same size as the original PCV valve used on the LSx Vette engines.

It would be nice to hear from anyone who has tried one and what differences they have seen on catch can accumulations and intake manifold oiling ... and especially oil residue in the fresh air line that goes from the valve cover to the throttle body.

I'm wondering if the fixed valve flows enough during WOT ... if not, it could cause more oil vapors to backflow down the fresh air line.

Bob CTS

Good info post, thanks

Bill Curlee

I would be willing to try it to see if it makes a difference. I consume very little oil but in the case of oil in the combustion process. LESS IS BETTER)

BC

HollywoodFRC

After reading the above earlier this year, switched to the fixed orifice PCV valve. No change in oil consumption which was minimal with the old type. So I guess it works OK, no issues so far.

7LitreC5

SDPC sent me one of those in the crate with my 427. It seems to work well. I checked my catch can after the first 1000 miles and there was only about a tablespoon of oil in the can.

Oldvetter

I have it installed in my car to prevent an oily intake manifold, even though my car uses no oil.

BTW, the part number is PCV Valve 12572717

People have reported that it decreases the oil in their catch cans.

A lot of LS1 sites recommend using it. It actually simulates the late year Z06 pcv setup.

I have also driven over 6,500 miles with it and have done an oil analysis, no difference in oil from stock pcv valve (this means it works okay and no fumes condense/accumulate in the oil).

See my post:

http://forums.corvetteforum.com/show...ight=pcv+valve

One person had this result: but only 4 ml of oil after 556 miles (0.01 ml/mile) with the fixed orifice vs. about 3 ml in only 100 (0.03 ml/mile)miles on the stock PCV valve. So the fixed orifice reduced oil consumption to 1/3 of the stock in only 1/5 of mileage (this would equate to a 1/15 decrease).

ArKay99

One very interesting line in the info provided was this one - "The original equipment valve may promote a siphoning of the oil back into the intake manifold where it would be consumed through the combustion process."
I have my catch can after my pcv valve mounted on the frame up in front of the radiator. It does collect oil, but it is slightly lower than the valley cover. That means the oil has gravity working with it coming into the can and against it coming out, but if a siphoning effect is occuring I'm wondering if moving it where it is higher would help more.
---
Also, I'm wondering if I have to use one of these with the LS2 I'm going to be running.

ZeeOSix

Oldvetter -- good info, and thanks for that other link ... I check that out too.

I was wondering if the fixed orifice valve would cut flow down too much and cause more contaminates in the oil, but your data on the oil analysis is good info on this issue.

Dave68

I guess my question is - Why is this NOT specified for the LS1? Could it be that a fixed orifice cannot flow as well under WOT conditions? This may not be too important for an SUV or truck, but a C5? Mmmmmm....

Y2Kvert4me

I would doubt that, since this style PCV first appeared on 2004 LS1/6 engines from the factory.

Dave68

Fair enough, but why doesn't the above-mentioned "Excessive Oil Consumption" bulletin include earlier year C5s?

ZeeOSix

Yes, I noticed and mentioned the application list did not address Corvettes. I'm wondering why also, since we all know that the 2004+ LSx switched over to the LS6 style valley cover with the 2.5 mm (1/10th inch) fixed orifice PCV system.

crazyburner

It is part of maintaining the PCV valve is replaced in five minutes

3 vettes

i installed this on my 99 in april.i would lose about 1/2 quart in 3,000 miles before with the stock pcv valve.since installing it my oil has been full after 3,000 miles and that includes many wot passes at 11.30.it definitely works.no residue in the intake either

allmee

I too am wondering why the Corvette is not mentioned in that service document. Obviously the smaller hole will cut down on the vacume & will draw less oil through the system. I am a little skeptical though about using it.

Dave68

Actually, when you increase restriction beyond the vacuum source, you increase vacuum pressure. However, as you mentioned, flow will be reduced, possibly resulting in less oil reaching the intake.

c5_4_me

so, is the fixed orifice PCV valve "Dave68 Approved"?



i would honestly like to know your opinion, Dave, as you seem to be well-versed in this topic.

BATM4N